Some embodiments described herein relate generally to methods and apparatus for optical communication. In particular, but not by way of limitation, some embodiments described herein relate to methods and apparatus for performance monitoring of coherent optical communication system at various baud rates.
With the increase in the amount of data to be communicated, optical communication systems have evolved to operate at higher data rates. For instance, some recent optical communication systems operate in the 100 gigabits per second (Gbps) range. Most long-haul optical communication systems use optical amplifiers to compensate for the attenuation introduced by optical fiber. While the optical signal is boosted, noise is also added, which can limit the transmission distance. Therefore, it is desirable to monitor the optical signal noise ratio (OSNR) of a coherent optical receiver. Known systems that can monitor the performance of a coherent optical receiver, however, are expensive and complex.
The U.S. patent application Ser. No. 15/197,646 discusses methods and apparatus to predict and monitor performance of a coherent optical transceiver at a fixed baud rate (e.g., 32 GHz) and with a modulation format(s) (e.g., a polarization-multiplexed quadrature-phase-shift-keying (PM-QPSK)).
Accordingly, a need exists for improved and simplified methods and apparatus to monitor performance of a coherent optical receiver at various baud rates.